Or why is it not a simple shell call to Imagemagick?

Then it needs a server

Not if you port the shell and OS and ImageMagick to WASM first!

ImageMagick in Wasm lets you do lots of nifty stuff client-side. Here's a photocopy simulation thingie I made for instance: https://photocopy.fuglede.dk/

That is fun indeed :) Good effect!

It can pull images from a domain. That would be difficult (since for client-side rendered sites it would require loading the site in a sandboxed environment) or impossible (if the site actively prevents that using CORS or similar, or if it happens to include scripts which expect to be run in a normal environment).

Yup totally fair - would likely require you upload the images manually for pure client-side.

You might still be able to offset a portion of the compute by just figuring out the URLs of the images on the back-end, sending that list to the client, which would then download and do the optimization / resizing.

There is also the ability to run things like Playwright on the edge a la Cloudflare Workers. You can fallback to rendering JS required sites through that and do clientside imagemagick WASM shenanigans on the client once the worker returns direct links to all the images.

> Write it in...

I look forward to your version of this service, also to be provided for free, right? And for your sake, hopefully you won't have people in the comments demanding that you completely redo your project in the special way that suits them.

> Long term, how do you intend to sustain the service if users become dependent on it and need to use it at scale? ...

Is what I was responding to. Wasn't criticizing the posted product implementation choices or demanding a rewrite. I see how it could be read that way, which is unfortunate.

Parent comment asked a number of questions that all suggested a server was a requirement. If scale becomes any issue for a service like this, there are approaches other than shutting down the service due to server / maintenance costs.